Machine for stretch forming mandrel supported tube-like elongated stock



. 3,025,904 MACHINE FOR STRETCH FORMING MANDREL SUPPORTED R. F'; DEMARCO March 20, 1962' TUBE-LIKE ELONGATED STOCK 4.Sheets-Sheet 1 FiledMarch 1, 1960 INVENTOR.

Poss/er f. DEM/4260 March 20,1962

R. -F. DE MARCO MACHINE FOR STRETCH FORMING MANDREL. SUPPORTED TUBE-LIKEELONGATED STOCK Y 4 Sheets-Sheet 2 Filed March 1, 1960 INVENTOR.

205527 F 06 Mmeao In I ATTO/PNfV.

DE MARCO, I

. R. F. 3,025,904 MACHINE FOR STRETCH FORMING MANDREL SUPPORTED March20, 1962 TUBE-LIKE ELONGATED STOCK 4 Sheets-Sheet 3 Filed March 1, 1960INVENTOR.

05597 A '05 Mxwco ATTbR/VEK March 20,1962 R.- F. DE MA'RCO- 3,025,904 IMACHINE FOR STRETCH FORMING MANDREL SUPPORTED I TUBE-LIKE ELONGATEDSTOCK Filed March l, 1960 4 Sheets-Sheet 4 5" EQI INVENTOR. Passer ffifM/wco BY Y . 2 ATTORNEY;

atent @hiee Patented Mar. 20, 19:32

3,025,904 MACHINE FOR STRETCH FGRMING MANDREL SUPPORTED TUBE-LIKEELONGATEE STQCK Robert F. De Marco, Mentor, Qhio, assignor to The CyrilBath Company, Solon, ()hio, a corporation of Ohio Filed Mar. 1, 196%,Ser. No. 12,161 7 Claims. (Cl. 153-32) This invention relates to stretchforming machines and particularly to a stretch forming machine forforming elongated tube-like metal stock while the stock is internallysupported by a mandrel to prevent its buckling and collapsing.

More specifically, the invention relates to a stretch forming machinehaving a gripping head arranged to grip one end of a length of tubularstock for applying endwise tension thereto for stretch forming, the headbeing combined with a mandrel arranged to be slid free end foremost intothe stock through the end of the stock and through the gripping head,and having a portion spaced from the free end and arranged to occupy theportion of the stock gripped by the gripping head for resisting thecollapse of the gripped portion of the stock, thereby assuring effectivegripping of the gripped portion of the stock by the head.

Another specific object is to provide, in such a mandrel and stretchhead combination, means for advancing the mandrel into the stock throughthe end of the stock after the end portion of the stock is disposed inposition for gripping by the head but before the gripping operation, togrip the end portion of the stock with the man drel therein after themandrel is fully inserted in the stock and maintain the grip thereonduring the forming operation, and then to release the stock and withdrawthe mandrel from the stock through the gripping head and end of thestock.

Another specific object is to provide means in such a machine forforming serpentine bends in the lengths of stock.

Various other objects and advantages will become apparent from thefollowing description wherein reference is made to the drawings, inwhich:

FIG. 1 is a top plan view of a machine embodying the principles of thepresent invention, part thereof being shown in section as indicated bythe line 1-1 of FIG. 2;

FIG. 2 is a front elevation, partly in section, of the machineillustrated in FIG. 1;

FIG. 3 is a vertical sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is an enlarged fragmentary top plan View of the right endgripping head and mandrel support, showing the cooperation therebetween;

FIG. 5 is a left end elevation of the gripping head and mandrel supportillustrated in FIG. 4;

FIG. 6 is an elevational view taken on a line indicated at 6-6 in PEG.5;

FIG. 7 is a top plan view illustrating a tube-like article formed fromtube-like stock on the machine;

FIG. 8 is a cross sectional view of the article taken on the line 88 ofFIG. 7; and

FIG. 9 is a diagrammatic illustration of a form of fiuid pressurecircuit suitable for operation of the machine.

Referring first to FIGS. 1 through 3, the machine illustrated is one forforming so-called tubular stock, such as true tubes which areperipherally continuous in cross section; open sided stock such as beadtrim and bumpers for automobiles; and other types of concavoconvex stockwhich must be reinforced by a mandrel during stretch forming. Themachine comprises a supporting frame 1 arranged preferably horizontallyfor convenience in operation of the machine. Carried by the frame 1 isan upright column 2 on which are mounted swinging arms 3 and 3a,respectively. The arm 3 is provided with suitable bearing portions 4 atits inner end which engage the post 2 and support the arm 3 for swingingabout the upright axis of the post. The arm 3a is provided with likehearing portions 4a. Since these arms 3 and 3a, and their operatingparts and mechanisrns carried thereby are the same in form and functionin most respects, only the arm 3 and its associated parts and mechanismsare described in detail, except as to parts or mechanisms which differfrom those of the arm 3.

At its outer end, the arm 3 is provided with suitable rollers 5 whichengage a track 6 carried on a support 7 which, in turn, is carried onthe frame 1. The support 7 also carries an overhanging guide 8 disposedabove the rollers with slight operating clearance while the rollers arein engagement with the track 6 so that the guide 8 and track 6 canconstrain the arm 3 from rocking transversely of the axis of the post 2in a vertical plane.

The positions of the arms for starting the forming operation on a lengthof stock are somewhat forward of the position shown in FIG. 1. Forswinging the arms from their starting position rearwardly the requisitedistance to form the stock, the arms 3 and 3a are provided with linksit), respectively. Each link 10 is pivotally connected by a pivot 11 toits associated arm and is pivotally connected by a pivot 12. to a commondriving carriage 13. The carriage 13 is mounted for sliding movementalong a trackway 14 forwardly and rearwardly of the frame 1 and, in sodoing, swings the arms forwardly and then from their forward positionsto their rearmost positions.

In order to drive the carriage, suitable power means are provided. Thepower means, in the form illustrated, comprises a reversible hydraulicpiston and cylinder assemblage 15 including a cylinder 16 mounted onhorizontal trunnions 17 on the carriage 13. The assemblage also includesa piston 18 having a piston rod 19 which is connected at its rear end bya pivot 20 to a suitable anchor bracket 21 on the frame. Thus, uponoperating the piston and cylinder assemblage 15 to extended position,the arms 3 and 3a are swung to their forwardmost positions,respectively, and upon operating the assemblage 15 to retractedposition, the arms 3 and 3a are swung to their rearmost positions,respectively.

Supported on the frame 1 is a platform 25 which, in

turn, supports a side face die 26. The contour of the side face of thedie is, of course, determined by the shape to be imparted to the lengthof stock to be stretch formed. Combined stretch forming and mandreloperating mechanisms are mounted on the arms 3 and 3a, respectively.

Referring first to the mechanism for the arm 3, this assemblagecomprises a carriage 30 mounted on the arm for reciprocation therealongand driven by a reversible hydraulic piston and cylinder assemblage 31.The assemblage 31 includes a cylinder 32 in which is reciprocable apiston 33 having a piston rod 34. The head end of the cylinder 32 ispivotally connected by a pivot 35 to a rigid portion of the arm 3. Thepiston rod 34 is connected to a bracket 36 which is rigid with thecarriage 30.

Mounted on the carriage 30 for swinging about an upright axis is ahorizontally extending supporting platform 37. In order to mount theplatform for such swinging, it it provided with dependent trunnion 38which is rotatably mounted in a suitable bearing 39 carried on thecarriage 34 A suitable weight supporting skid pad 44) is provided on thecarriage 30 and engages a complementary pad 41 on the underside of theplatform 37 for relieving the platform of overhanging stresses andloads. A suitable hold-down bracket 42 is provided on the platform 37and is arranged to engage the underside of the margin of the skid pad 4%for preventing deflection of the platform 37 vertically.

Mounted on the platform 37 is an upright supporting post 45 which, atits upper end, carries a gripping head 46 for gripping the one end ofthe length of stock. Also mounted on the platform 37 is a mandrel slide.8 arranged for sliding movement in suitable guideways 49 mounted infixed position on the supporting platform 37 so as to be reeiprocableendwise of the platform 37. Suitable guide rods 50 are connected tobrackets 51 and 52 on the platform 37 and engage a suitable slidebearing, as indicated at 53, in the mandrel slide for guiding themandrel for sliding horizontally along a lineal path endwise of theplatform 37 along its guideway 49.

In order to reciprocate the mandrel slide along said path, a suitablereversible hydraulic piston and cylinder assemblage 55 is provided. Thisassemblage includes a cylinder 56 with a piston 57 reciprocable thereinand provided with a piston rod 58. The rod 58 is connected to a forwarddependent end portion 59 of the mandrel slide 48. Since the assemblageis reversible, the slide can be projected forwardly or retracted,selectively. At its outermost end, the slide 48 is provided with amandrel head 60 carried on a suitable upright supporting pedestal 61.The mandrel head 60 is secured to one end of a mandrel 62. The mandrelmay be in the form of .a plurality of nylon discs 63 of the requiredoutline to fit the internal cross section of the stock to be formed, andheld together in face to face alignment by a suitable Wire 64 so thatthe mandrel can bend and warp and curve and adjust itself to variousbends which may be formed in the stock during the forming operation. Thehead 60 of the mandrel is firm and rigid and is so arranged that withthe mandrel inserted in the stock the portion of the stock gripped bythe gripping head 46 contains the mandrel head and is thereby preventedfrom collapse by the gripping head 46, thereby assuring an effectivegrip on the stock.

The mandrel is carried in a suitable guide 66 which has a passagetherethrough to fit the mandrel and support it for endwise slidingmovement.

When the mandrel head 69 is in the fully retracted position, the entryor free end 67 of the mandrel is within the stretch forming grippinghead ready to be inserted into the stock through the end of the stockwhen the stock is inserted into the gripping head 46. This structure isbest illustrated in FIGS. 4 through 6. As mentioned heretofore, thegripping head 46 is mounted on the support 45 and includes a stationarygripper jaw 70 and a movable gripper jaw 71 supported in a suitablesupporting plate 72. The jaw 71 and plate 72 have cooperating slidesurfaces 73 which are biased the direction of pull to be applied on thestock so that as the jaw 71 moves toward the gripping position, or tothe left in FIG. 4, it moves inwardly into gripping relation to thestock. The movement necessary for engaging the stock is usually quitelimited depending upon the thickness of the stock. The gripping faces ofthe jaws 70 and 71 are shaped to conform to the stock, as indicated at74 and 75, respectively, and to engage a substantial area of the stock Sof which a cross section is illustrated in FIGS. and 8. In order to movethe jaw 71 to and from gripping positions, a reversible piston andcylinder assemblage 76 having a piston 77 and a piston rod 78 is fixedlymounted on the supporting plate 72. The rod 78 is connected to the jaw71.

In operation, the jaws 70 and 71 are separated, the end portion of thetubular stock is moved endwise to a position therebetween, and then thepiston and cylinder P assemblage 55 is operated to advance the mandrelfree end foremost into the stock until the rigid head 60 of the mandrelis within the stock at a location endwise of the stock between the jaws70 and 71. At this time, the jaw 71 is advanced, and the jaws clamp theend portion of the stock tightly against the mandrel and exertssufficient gripping pressure for the stretch forming of the stock, themandrel head 68 preventing deformation of the stock at the grippedportion.

In the particular form illustrated, the portion of the die 26 isrelatively straight and, therefore, a very short mandrel may be used onthe right-hand arm 3 as it need only be inserted into the stock slightlybeyond the bend, as indicated by the radius line Y in FIG. 1. Thelefthand arm 3a is provided with a structure which is similar in allrespects to that heretofore described, the only difference being thatthe platform 84), the mandrel slide 81, the mandrel guide 82, themandrel 83, are longer than their counterparts, the support 37, slide48, guide 66, and mandrel 62 on the arm 3. This is because at the peakpoint of the die, as indicated at Z in FIG. 1, there is a bend and thestock has to be supported at this particular location. Accordingly, themandrel 83 is made longer so that when fully inserted into the stock,its free end reaches just to or very slightly beyond the point Z in adirection toward the mandrel 63.

Thus, in FIG. 1, the left-hand portion of the stock being formed ismandrel supported interiorly from just to the right of the point Zentirely to the left-hand end of the face of the die 26. The mandrel 83has a head 84 corresponding to the head 60 of the mandrel 62. As can beseen from FIGS. 7 and 8, the stock to be formed is first bent convexlyforwardly of the machine and then near its end is reversely bent so thatit is a compound or sinuous curve. For this reverse bending, there aremounted on the die 26, at opposite ends of the side face, respectively,and in spaced relation thereabove, supporting plates 85. These platesare supported by suitable bolts and sleeves 86. Reverse dies 87 arearranged to be disposed in the plane of the die 26. The dies 87 aresupported on suitable guide rods 88 which protrude from the bottoms ofthe dies 87 a short distance, as indicated at 89. The platform 25 isprovided with suitable bores 90 adjacent the opposite ends of the die 26which receive the lower ends 89 of the rods 38 when the dies 87 rest onthe upper surface of the platform 25, and thus with their faces disposedalongside the side face of the die 26. Suitable reversible hydraulicpiston and cylinder assemblages 91, each including a piston 92 having apiston rod 93, are mounted on the plates with their rods 93 connected tothe dies 87, respectively. These assemblages are operable to lift andlower the reverse dies 87, respectively, and to press the dies 87 firmlydownwardly against the platform 25 when desired whereon they are heldfixedly in position transversely of the platform by the lower ends 89 ofthe guide rods 88 engaging the bores in the platform 25.

In the operation of the machine, the arms are swung sufficientlyforwardly, by their piston and cylinder assemblages 31, so that thegripping heads 46 and 94 are aligned with each other in a straight lineforwardly of the peak Z of the die 26. In this position, a length oftubular stock is inserted endwise into the gripping heads 46 and 94.While so disposed, the slides 48 and 81 are moved to extended positionby their associated assemblages 55 so that the mandrels 62 and 83 enterthe ends of the stock and are advanced endwise into the interior of thestock, the free or leading end of the mandrel 62 passing just beyond theradius line Y, and the free end of the mandrel 83 passing just beyondthe peak Z. When the mandrels are in this position, the heads 60 and 84are disposed endwise in the end portions of the stock which are locatedbetween the jaws of the associated gripping heads 60 and Y84,respectively. Thereupon the jaws of the gripping heads 46 and 94 areoperated by their assemblages 76 to clamp the stock firmly against therigid heads 69 and 84 of the mandrels, the head of each mandrel actingto transmit the force applied by each of its associated jaws to itsassociated opposed jaw. With the parts in this condition, the piston andcylinder assemblages 15 are operated to cause the arms to swingrearwardly, thus laying the stock along the side face of the die 26 fromthe peak Z toward radius lines, such as indicated at the radius line Y,at opposite ends, and preferably entirely to the end of the side face ofthe die 26. When the stock is held in this position, the piston andcylinder assemblages 91 are operated to lower the reverse dies 87. Whenthe dies 87 are lowered and seated, the piston and cylinder assemblagesare operated to swing the arms 3 and 3a forwardly, thus imparting thereverse bend in the stock by bending it forwardly around the dies 87.This reverse bending operation is described broadly in US. LettersPatent No. 2,444,719, issued July 6, 1948, to Cyril J. Bath.

After the stock has been thus reversely bent, the stretch jaws of thehead 46 are released and the mandrel 62 is withdrawn by operation of itsassociated slide 48 by its assemblage 55. Next, the jaws of the head 94are released and the mandrel 83 is withdrawn by its slide 81. Afterwithdrawal of the mandrels, then the stretch heads are retracted by theretraction of the platforms 37 and 80 by the assemblages 15, whereuponthe stock is released for removal from the machine.

Generally, suitable cut-off mechanisms may be provided in the properposition on the supporting plates 85 for cutting off the stock after ithas been released by the stretch forming heads and mandrels, if desired.

A conventional knock-out mechanism may be provided for moving the pieceforwardly out of position on the die 26.

For purposes of illustration, the invention 'has been described asoperated hydraulically, but pneumatic fluid pressure may be used in lieuthereof.

Referring specifically to the hydraulic circuit illustrated in FIG. 9,the pressure fluid is supplied by a suitable pump 97 driven by a motor98. The pump 97 has a pressure line 99 which is connected to a suitablevalve 100 by which it is connectable to opposite ends of the piston andcylinder assemblage 15, selectively. The valve 100, as illustrated, is athree-way valve and in one position admits pressure fluid to the headend of the cylinder and vents the rod end of the cylinder to a sump. Inanother position, it reverses this connection. In an intermediateposition, it connects both ends of the cylinder to a sump and blocks thepressure fluid from the pump, thus permitting the retraction andextension of the assemblage 15 by hand. The valve 100 may be remotelycontrolled by suitable solenoids 101 from a central control panel, ifdesired.

Similar valves are arranged for the other piston and cylinderassemblages and are operable in like manner. For example, valves 102 areprovided for the cylinders 76 which operate the clamping jaws. Valves103 are provided for the cylinder assemblages 55 which operate themandrels 62 and 83, and valves 104 are provided for operating theasemblages 31 for the platforms 37 and 80. These valves are conventionalvalves and operate in the well known manner.

It has been found that, with this type of operation, lengths of tubularstock, such, for example, as the stock S illustrated in FIGS. 7 and 8,can be stretch formed readily. Likewise, if desired, peripherally closedtubular stock may be formed. In all such types of tubular stock,requiring the support of a mandrel during forming, the present machinecan be employed, an important feature being that the mandrel is properlyinsertable through the stretch forming head and has a rigid head which,when the stock is gripped under pressure by the jaws of the stretchheads, prevents collapse of the stock at the gripped portion and assures(good gripping pressure for stretch forming.

The operation of the machine may be rendered automatic, semi-automatic,or manual, as desired, by the usual control cams and the like. Forbrevity, the machine is described and claimed herein as positioned withthe swinging axis of the arms upright, using such words G as upright,horizontal, vertical, and the like. Those words are used merely todescribe relative positions of various parts, not their absolutepositions.

Having thus described my invention, I claim:

1. In a stretch forming apparatus, a die support, a side face diemounted thereon, gripping means to hold a length of stock, with oneportion, which is spaced from one end of the stock, in fixed positionrelative to the die, a power operated stretch forming assembly includinga stretch head operable to grip said one end of the stock and applyendwise tension to the stock, means to cause relative swinging movementof the head and die in a direction transversely of the die for layingthe stock progressively on the side face of the die in a directiontoward said head while the stock is held under tension by the head,opposed separable clamping jaws in the head operable by movementrelative to each other to grip and release the stock, respectively, saidhead having a passage extending between the jaws with an open inner endand an open outer end, the inner end being at the side of the jawstoward the die and the outer end being at the opposite side of the jaws,means to operate the jaws, an elongated mandrel, mandrel supportingmeans supporting the mandrel for endwise movement of the mandrelrelative to the stretch head from a retracted position, in which atleast part of the mandrel is disposed outwardly, endwise of saidpassage, from the outer end of the passage, in a direction toward theinner end of the passage to an extended position in which one portion ofthe mandrel lies in the passage between the jaws and another portionprojects beyond the inner end of the passage so as to lie within thestock selectively, and said one portion between the jaws lies inengagement with the stock when the mandrel is in the extended positionand supports the stock against collapse by the force applied by thejaws.

2. The apparatus according to claim 1 wherein said one portion of themandrel is a rigid head.

3. The apparatus according to claim 2 wherein the mandrel is flexiblefor the major portion of its length beyond said rigid head.

4. The apparatus according to claim 1 wherein power means are connectedto the mandrel supporting means and are operable to move the mandrel toextended and retracted positions, selectively.

5. The apparatus according to claim 4 wherein said one portion of themandrel is a rigid head, the supporting means including a slide and amember connecting the rigid head to the slide in spaced relation to theslide, said apparatus including an elongated hollow mandrel guide, saidguide having a passage at one side extending along at least the majorportion of its length, said mandrel and rigid head being within theguide, and said member extending through said passage and being movabletherealong upon movement of the slide lengthwise of the guide.

6. In a stretch forming machine, a frame, a horizontal die supportmounted thereon, a side face die mounted on the support, means to hold alength of stock with one portion, which is spaced from one end of thestock, in fixed position relative to the die, an arm, means supportingthe arm for swinging about a fixed upright axis, a platform mounted onthe arm for swinging relative to the arm about an upright axis, poweroperated stretch forming means connected to the platform and including astock gripping head having stock gripping jaws for gripping said one endof the length of stock, a horizontal slide on the platform, a mandrelhead on the slide, a mandrel connected at one end to the mandrel headand positioned to be moved thereby endwise between and beyond the jawsin a direction toward the other end of the stock so as to lie alongsideat least one wall portion of the stock with the mandrel head between thejaws and lying alongside at least said wall portion of the stock, meansto operate the jaws to clamp the stock when the mandrel head is betweenthe jaws, and power means to 7 swing the arm in opposite directionsabout its axis, selec tively.

7. In a stretch forming machine, a frame, a horizontal die supportmounted thereon, a die on the support, a pair of arms pivotally mountedon the frame for swinging horizontally toward each other, said diehaving an intermediate bend spaced from its ends, stretch formingassemblages on the arms, respectively, each assemblage in cluding astretch head having stock gripping separable jaws and means foroperating the jaws, said heads being arranged to grip opposite ends of alength of stock for transmitting tension thereto from the assemblagesfor tensioning the stock endwise, mandrel supports mounted on the arms,respectively, for movement toward and away from the heads, mandrels onthe supports, respectively, and movable thereby relative to the headsendwise References Cited in the file of this patent UNITED STATESPATENTS 2,357,027 Seifried Aug. 29, 1944 2,729,265 Jones Jan. 3,19562,889,864 Bowser June 19, 1959 nay-a.

